The present state-of-the art technology is known to make extensive use of evaporable getters based on alkaline-earth metals, such as barium, calcium, strontium.
The getters of the above type feature a fairly small sorption capacity margin due to the insignificant amounts of active metal included in their composition.
The use of the evaporable getters causes electronic devices to develop such defects as leakages, spurious capacitances and high-frequency losses, which results from the spraying of the vaporized metal onto undesired areas of the device. Furthermore, an inadequate degree of mechanical strength exhibited by the residue of metal evaporation causes the devices to develop such objectionable phenomena as sparking, break-downs and short-circuits brought about by the presence of extraneous particles from the getter.
The evaporable getters offer a narrow range of operating temperatures (from 20.degree. to 200.degree. C.), which considerably confines their field of application.
In order to produce a metal mirror with required sorption and mechanical properties it is necessary to meet a variety of different conditions, such as evaporation temperatures, distance between the getter and the surface on which the vaporized metal should condense, gaseous atmosphere in the device, amounts of the vaporized metal and so forth.
To a considerably larger degree today's technology requirements are satisfied with the advent of getters of a new type, i.e. the porous non-evaporable getters differing essentially from the evaporable getters in the mechanism of gas bonding which takes place due to the diffusion of gases into the metal and the formation of solid solutions. This results in fairly high sorption rates and large porous getter sorption capacities.
The non-evaporable getters may be located at any spot of the device and in any amount inasmuch as this is not accompanied by negative phenomena in the device owing to the getters as is often the case whenever the spray getters are involved.
The getters currently employed in the devices of various classes and designations are expected to display high sorption and mechanical properties over a broad range of temperatures.
In particular, known is a non-evaporable getter representing a sintered mixture of a zirconium-aluminum alloy and zirconium powder (see U.S.S.R. Pat. No. 640685).
The above non-evaporable getter features the highest sorption properties at a temperature of about 400.degree. C.
However, beyond this temperature range, as stated in the Specification, the sorption properties of the getter are deteriorating.
The manufacturing process for the non-evaporable getter under consideration is characterized by increased explosion and fire hazards which are engendered by the presence of zirconium in the composition.
The non-evaporable getter of the above-specified composition suffers from an inadequate degree of mechanical strength due to its insufficient compressibility brought about by the presence of the alloy in the composition thereof. As a consequence, the device may eventually develop such severe defects as sparking, break-downs and short circuits caused by the presence of extraneous particles.
A decreased level of explosion and fire hazards, as compared to the foregoing nonspray getter, is exhibited by a non-evaporable getter containing titanium and an alloy of zirconium and vanadium (see U.S.S.R. Author's Certificate No. 693456).
A decrease in the level of explosion and fire hazards is achieved by reducing the content of zirconium in the composition of the getter and by using zirconium in the form of an alloy.
Sorption properties of this getter meet all the requirements at temperatures up to 800.degree. C.
At temperatures in excess of 800.degree. C. the titanium is recrystallized and the physical and chemical properties of the getter are changed resulting in a decrease in its sorption properties.
Furthermore, due to the presence of zirconium in the composition of the non-evaporable getter some of the stages of its manufacturing process still do not exclude potential explosion and fire hazards.
The non-evaporable getter of the above composition also suffers from an inadequate degree of mechanical strength due to its insufficient compressibility resulting from the presence of the alloy in the getter composition and, consequently, may cause the devices to develop such defects as sparking and break-downs.
By far the better sorption properties at temperatures in excess of 800.degree. C. are displayed by a non-evaporable getter containing titanium, zirconium and tantalum, i.e. a refractory metal belonging to Group V of the Periodic System of elements (see U.S.S.R. Author's Certificate No. 336719).
An increase in the upper temperature limit, at which the getter maintains its high sorption properties, is ensured owing to the introduction of a refractory metal into its composition, in particular tantalum. Tantalum being distributed uniformly among the active particles of the getter prevents their fusion during the process of sintering and at the same time contributes to an increase of the porosity and of the active surface of the non-evaporable getter. As a consequence, the getter preserves its high sorption properties at higher temperature values.
However, as was found, the sorption and mechanical properties of the above getter do not fully meet the requirements currently imposed on the getters for use in the electronic devices, such as the increased reliability and longevity requirements, in particular in terms of the sorption of different gases at low temperatures (20.degree. to 500.degree. C.) and the resistance to vibration effects at frequencies in excess of 1000 hz.
Moreover, the production operations associated with the manufacture of the non-evaporable getters of the above composition also involve explosion and fire hazards, which results from the presence of zirconium in the composition.